Large magnetocaloric effect, moment, and coercivity enhancement after coating Ni nanoparticles with Ag.
Chemphyschem
; 15(8): 1619-23, 2014 Jun 06.
Article
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| MEDLINE
| ID: mdl-24615843
ABSTRACT
We observe a large magnetocaloric effect in monodisperse Ni and Ni(core)Ag(shell) nanoparticles in the superparamagnetic region. The organically passivated Ni nanospheres show a large magnetic entropy change of 0.9 J kg(-1) K for a 3 T magnetic field change. In comparison to the surfactant-coated Ni nanoparticles, the Ni(core)Ag(shell) nanoparticles show an enhanced coercivity, magnetization, and magnetocaloric effect (1.3 kg K for a 3 T magnetic field change). The coercivity at 10 K increases from 360 Oe for Ni nanoparticles to nearly 610 Oe for Ni(core)Ag(shell) particles. This large enhancement is attributed to the enhanced inter-particle interaction, which is mediated by the metallic shell, over the relatively weaker dipolar interaction in the surfactant-coated Ni nanoparticles, and to modification of the surface spin structure.
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